Ever since Silvio Berlusconi was re-elected to a third term of office as Prime Minister of Italy, left-wing commentators and activists have bemoaned the failures of the ineffective opposition parties. Now they have found an unlikely heroine in Berlusconi's daughter Barbara, who has taken on her father with an intervention that suggests a promising political future - on the left.

Ms Berlusconi is 24, rich, good-looking, and has something of a history when it comes to not toeing the family line. When she was 21, she said would turn off the television if she found her children tuned into a variety show from Berlusconi's Mediaset network. She has also refused to join the Forza Italia party that propelled Berlusconi to power. And last week, to the delight of her father's critics, she called for a clampdown on the rampant conflicts of interest undermining business and politics, a battle cry that could rattle her father as he divides his time between running the country and controlling an empire spanning TV stations, banking, publishing and football.

'I am convinced that the conflict-of-interest question needs to be regulated,' said Barbara Berlusconi, who is wrapping up a thesis on ethics in finance for a philosophy degree in Milan. In an interview with La Stampa last week, she admitted she was fighting a lonely battle, given the apparent lack of national interest. 'Voting has shown that Italians do not see this as necessary,' she said sadly. 'There is a need but no demand.'

Her words were pounced on by the hard-left daily Liberazione, which praised Barbara for doing a better job than 'the entire parliamentary opposition', and with bitter irony observed that in Italy the 'government and opposition are now contained in one family'.

Silvio Berlusconi has two sons and three daughters by two marriages. Marina, 42, from his first marriage, is a regular high entry in the Forbes 'most powerful women top 100'; Eleonora, Barbara's younger sister from the second marriage to Veronica Lario, has so far shown little interest in politics. But Lario, a former actress whom Berlusconi first encountered when she appeared topless in a Milan theatre production, has revealed liberal inclinations.

Lario has kept a low profile, declining to accompany Silvio on state visits while hinting that politics can be a sore topic at the Berlusconi breakfast table. In an interview with Micromega, a fiercely anti-Berlusconi publication, she attacked the war in Iraq in defiance of her husband, who sent troops there.

Barbara, Lario's increasingly influential elder daughter, is the co-founder of Milano Young, a charity set up by the offspring of some of Italy's wealthiest businessmen to send money to victims of Asia's 2004 tsunami. The group is rapidly becoming a fashionable meeting place for the young, wealthy and well-connected who want to enjoy life without betraying their social consciences. Recruits include Francesca Versace, of the fashion family; Paolo Ligresti, son of insurance magnate Salvatore; and Geronimo La Russa, son of Ignazio, Defence Minister in Berlusconi's government. The Milano Young website, featuring charity bashes and ski trips, is inviting members to a conference on business ethics next month.

'We need more rules for correct conduct, but also strong institutions to ensure that current laws are really respected,' Barbara says. Her comments are aimed at the meltdown in financial markets, but stand in stark contrast to her father's epic struggle with Italy's judges. Milan prosecutors are attempting to move ahead with a corruption trial involving Berlusconi and David Mills, estranged husband of British Olympics minister Tessa Jowell, while Berlusconi recently pushed through a measure granting the top four officials in Italian government, including himself, immunity from prosecution.

For now Barbara remains tight-lipped on whether she has buttonholed her father on the subject of conflicts of interest. 'We have not had the time yet, but he will be the first to see my thesis,' she said. Now a board member at Fininvest, the holding company founded by her father, she has a platform to preach her ideas in the business community, a tough task as Italy slips further down Transparency International's corruption index. Now ranked 55 on the list of the world's least corrupt countries, down from 41 last year, Italy is perceived as having less trustworthy politicians than Chile, South Korea or Costa Rica.

The Prime Minister's allies have tried to play down the prospect of a familial insurgency in Italian politics. According to Ignazio La Russa, father of Geronimo: 'Children of politicians or entrepreneurs, just like children of employees and workmen, all aspire to create a better world and should not be labelled "left-wing" as a result.'